The invention relates to a gas transport laser with longitudinal gas flow and complete integration of the components with at least one laser tube, where the laser gas is drawn off in the center of the respective laser tube, fed through a radial blower, a cooling system and a gas supply system and then supplied to the respective two ends of the laser tube, and where the laser tube is disposed on, and so as to extend perpendicularly to, the axis of the radial blower.
The efficiency of molecular lasers and in particular CO.sub.2 -lasers decreases with increased termperature in the laser gas. Among the reasons for this are the width of the fluorescence lines increasing with increasing temperature, the excitation energy being distributed to an increasing number of rotational levels, the amount of deactivating collisions increasing, the occupation of the end level of the laser because of thermal excitation increasing and thus the inversion decreasing (see K. Gurs, "Laser 75 Opto-Electronics", Munchen 1975, Conference Proceedings, pp. 30 to 37).
For this reason, a number of methods for keeping the temperature of a laser gas low have been developed. In connection with a particularly advantageous method the heat is bled off with the laser gas (in a gas transport laser). Lasers operating according to this method comprise an excitation zone with an adjacent or integrated optical resonator, from which gas is fed across coolers, and a pump.
Gas transport lasers are divided into those with longitudinal and those with transverse gas flow. In transverse systems the time spent by the excited active molecules in the laser resonator is comparitively short and in general shorter than their life. This results in an increase of the so-called saturation power. It can become greater than the actual power density in the laser resonator. This results in the excitation energy being bled off to a large degree together with the laser gas, thus not being transformed into laser output. Therefore gas transport lasers with transverse flow have a comparatively small efficiency which in general is less than 10%. Furthermore, excitation in transverse lasers is relatively inhomogeneous, which leads to adverse beam characteristics.
For this reason interest has in general increasingly been transferred to lasers with longitudinal gas flow. However, with these, too, correspondingly large amounts of heat must be bled off and large amounts of gas must be recirculated. Separate pumps and coolers, which are connected by tubing, are utilized with the known gas transport lasers with longitudinal gas flow. Therefore, the known lasers of this type are large and expensive. Their range of use is limited because of their bulkiness. Furthermore, the tubing causes a corresponding flow resistance. Because of this the efficiency of the systems is decreased, or particularly large pumps are required.
It has already been possible to overcome these disadvantages of the known gas transport lasers by a device in which the laser chamber is designed as a cooled pipe and disposed concentricaly within a circulating turbine (see German Published Patent Application DE-OS 31 21 372). However, this laser can only be realized with large structural expense (also see German Published Patent Application DE-OS 32 45 959). Moreover, these known lasers have the following disadvantages:
1. When applying high voltage to the electrode ring there is the possibility that there will not only be a gas discharge in the laser tube in the direction of flow, but also a breakdown in the opposite direction towards the housing or cooler. To avoid this, the electrode ring must be disposed far inside the laser tube and a long dead section (section free of excitation) must be tolerated.
2. Tubes of diameters greater than 25 mm must be used in connection with efficient longitudinal gas transport lasers, in which it is difficult to generate a uniform high voltage glow discharge. Some suggestions for improving homogeneity are known: According to Herziger et al (German Patent DE-PS 33 23 954) swirling with tangential feeding of the laser gas improves the uniformity of discharge. J.E. Harry and S. SN Saleh use segmented electrodes (Appl. Phys. Lett. 40, 1982, 359-361). In H. Sugawara et al the suggestion is found to shape the electrode ring support in a particular way (Rev. of Laser Eng. 9, Japan, 1981, pp. 21 to 30). These suggestions result in improvements but do not represent ideal solutions. A uniform discharge could be achieved with high-frequency excitation; however, the expense for this type of excitation, particularly with large laser output, appears to be unjustifiably large.
3. In the laser according to German DE 32 45 959 Al a combination of several lasers without the use of additional mirrors (deflection mirrors) is only possible if these lasers are combined in a longitudinal direction. This results in very long unwieldy systems.